We actually have four WoW accounts in the family. They are for myself, my wife and my 16 year old son and 12 year old daughter. My stepson plays Toontown online because even though he is 12 years old, he is Autistic and doesn't communicate very well.
My wife and I also play City of Heroes/Villains on occasion and have accounts for that game as well. She plays several
MUSHes as well. We also have an XBOX, PS2, and Gamecube in the house with various games and the kids each have a Nintendo DS.
World of Warcraft gets the most playtime though because we have met more people on that game and its very time consuming to get to the max level.